Add toggle to enable ambient packages (ztunnel, gateway-api, istio-cni)

General MR

Summary

Creates a global ambient flag at .Values.ambient, which if set to true:

• enables istio-cni, ztunnel, gateway-api
• configures Istio to support ambient mode
• opts in any packages deployed via packages to ambient mode:

Note: This does not currently opt-in any other core packages to ambient mode.

Relevant logs/screenshots

Linked Issue

issue

Upgrade Notices

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